/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Copyright 2018 Danny Robson <danny@nerdcruft.net>
 */

#include "sample.hpp"

#include "../point.hpp"

#include <random>


///////////////////////////////////////////////////////////////////////////////
std::vector<util::point2f>
util::geom::poisson_sample (util::extent2i area, float distance, int samples)
{
    std::vector<util::point2f> selected;

    std::vector<util::point2f> candidates (samples);
    std::uniform_real_distribution<float> dist_w (0, area.w);
    std::uniform_real_distribution<float> dist_h (0, area.h);
    std::random_device rd;
    std::default_random_engine gen;

    selected.push_back ({
        dist_w (gen),
        dist_h (gen),
    });

    auto min_distance = [&selected] (auto q) {
        float min_d = INFINITY;

        for (auto s: selected)
            if (auto s_d = util::distance2 (s, q); s_d < min_d)
                min_d = s_d;

        return min_d;
    };

    while (1) {
        util::point2f p;
        float d = -INFINITY;

        for (int i = 0; i < samples; ++i) {
            util::point2f candidate { dist_w (gen), dist_h (gen) };

            if (auto p_d = min_distance (candidate); p_d > d) {
                p = candidate;
                d = p_d;
            }
        }

        if (std::sqrt (d) < distance)
            break;

        selected.push_back (p);
    }

    return selected;
}